The instant invention relates to boat hull constructions and more particularly to a composite metal frame/foam core boat hull construction.
Over the past several years, the need for intermediate size (40-100 feet), high speed ferry vessels has grown significantly. However, existing boat constructions have been unable to provide the desired combination of weight, speed, safety and cost which is essential for the successful operation of such ferry services. In the past, fiberglass hulls have been utilized to provide light weight boats. However, the practical size limit of fiberglass hulls is about 65 feet. Furthermore, fiberglass hulls of greater than 40 feet require a multilayer fiberglass laminate construction which is extremely difficult to construct, and thus expensive. Another means of achieving a light weight hull construction is the use of composite metal/foam/fiberglass hull constructions which provide the combined features of lighter weight and safety, i.e. foam buoyancy. In this regard, the Blount U.S. Pat. No. 4,365,580 represents the closest prior art to the present invention of which the applicant is aware. The Blount patent discloses a composite hull construction for boats including a rigid box-like cockpit structure which provides the main structural element of the boat, and a synthetic foam core bonded to the exterior surfaces of the box-like structure. The exterior surface of the foam is formed to define the outer configuration of the hull and a layer of resin impregnated glass fiber material is layed-up over the foam to provide a protective outer covering. While effective, there is nevertheless a need for creating hull structures which are even lighter in weight, and more structurally sound than the previous designs.
The instant invention provides a composite hull construction including a metallic skeletal frame of truss-like configuration. The frame includes a longitudinally extending keel plate, first and second side wall structures extending upwardly from opposing side edges of the keel plate assembly, and a top wall structure extending between upper portions of the first and second side wall structures. The side walls and top walls are formed in discrete truss-like frame sections separated by vertical dividing walls. A synthetic foam shell entirely encapsulates the frame elements of the side and top wall frame structures and covers the interior of the keel plate assembly. Preferably, the foam shell is formed by applying three separate layers of polyurethane foam materials over the frame elements until they are fully encapsulated. The outer layer of foam is about 0.5 inches thick and comprises a foam composition having a density of about 30 pounds per square foot, the intermediate layer is about 1.0 inch thick and comprises a foam composition having a density of about 10 pounds per square foot, and the inner layer is about 2-3 inches thick and comprises a foam composition having a density of about 2 pounds per square foot. Once cured, the rigid foam shell binds the frame elements in position and increases the strength of the skeletal frame in compression so that the wall structures are prevented from buckling under a compressive load. The foam encapsulation enables the entire frame structure and individual truss or frame elements to be fabricated from lighter weight materials than if the frame elements were not encapsulated in foam. An exterior fiberglass skin covers the side walls and the top wall to provide a water resistant covering over the foam shell and frame. The fiberglass skin is stretched over the side walls and top walls with terminal edges of the fiberglass material keel secured within spline channel members attached to the keel plate. Alternatively, metallic plates can be secured over the side walls and top wall to provide an outer covering to the hull structure. The hull further incorporates a fire suppression system which provides compartmentalized fire suppression in the event of a fire on board. In this regard, the hull is divided into a plurality of separate compartments by solid dividing walls. The interior dividing walls in each compartment are provided with cut-outs which both reduce weight and allow air flow from section to section. A plurality of heat and/or smoke sensors are located within the compartments, and a central carbon dioxide source with gas lines to each compartment are provided for flooding carbon dioxide into the hull compartments upon detection of excess heat and/or smoke. The described hull construction allows intermediate size, light weight boats to be constructed at a reduced cost with better safety features, i.e. higher buoyancy.
Accordingly, among the objects of the instant invention are: the provision of a light weight, structurally sound hull construction; the provision of a low cost hull construction; the provision of a highly buoyant hull construction which is extremely safe and unlikely to sink in the event of an accident; the provision of a hull construction having an integrated fire suppression system built into each discrete hull compartment, the provision of a hull construction comprising an interior skeletal frame having the structural frame members encapsulated in a foam shell which adds structural integrity to the frame construction; the provision of a multilayer foam shell wherein an outer shell layer is formed from 30 lb./sq. ft foam, an intermediate layer is formed from 10 lb./sq. ft foam, and an inner layer is formed from 2 lb./sq. ft foam; and the provision of a hull construction wherein a fiberglass skin is secured within spline channels attached to the keel plate of the skeletal frame.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.